Much recent research has concerned development of organic corrosion inhibitors which can reduce reliance on the traditional inorganic inhibitors. Among the organic inhibitors successfully employed are numerous organic phosphonates. These compounds may generally be used without detrimental interference from other conventional water treatment additives. Phosphonic acid compounds have also been used in other fields for such purposes as flame retardants, plasticizers, lubricants, and surfactants.
It has long been known that an aqueous suspension of paraformaldehyde may be reacted with phosphorous trichloride or orthophosphorous acid to produce hydroxymethylphosphonic acid. Hydroxymethylphosphonic acid has been reported as useful in combination with zinc for corrosion control. It is also reportedly useful as an intermediate for the production of polyoxymethylene phosphonates which have utility as urethane foam flame proofers and plasticizers.
U.S. Pat. No. 3,970,729 discloses that phosphorous acid can be contacted with formaldehyde, or a formaldehyde condensate such as trioxane (a cyclic trimer of formaldehyde) or paraformaldehyde, ( a linear polymer of formaldehyde) to yield a hydroxymethylphosphonic acid intermediate that can then be contacted with certain alkylene oxides to yield di-polyoxyalkylene hydroxymethylphosphonates. These products are reportedly useful as stabilizers for polyester film, plasticizers, flame retardants, lubricants and hydraulic fluids.